In the existing 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short) Evolved Universal Mobile Telecommunications System (Universal Mobile Telecommunications System, UMTS for short) Terrestrial Radio Access (Evolved-UMTS Terrestrial Radio Access, E-UTRA for short) system, two modes, Frequency Division Duplexing (Frequency Division Duplexing, FDD for short) and Time Division Duplexing (Time Division Duplexing, TDD for short) are supported. In the Long Term Evolution (Long Term Evolution, LTE for short) system, a terminal receives downlink data and transmits uplink data on uplink and downlink resources respectively, according to an indication of Physical Downlink Control Channel (Physical Downlink Control Channel, PDCCH for short) sent by a base station. In a LTE FDD system, the maximum of number of Hybrid Automatic Repeat Request (Hybrid Automatic Repeat Request, HARQ for short) processes is 8, and synchronized adaptive or non-adaptive retransmission is adopted in uplink, and non-synchronized adaptive retransmission is adopted in downlink. In the LTE TDD system, the maximum of number of HARQ processes is 15.
Uplink data transmission is taken as an example. A base station sends a corresponding uplink resource indication (UL grant) on a PDCCH resource in subframe 0 to perform uplink subframe scheduling. Upon receiving the PDCCH, the terminal acquires resource position and corresponding transmission configuration indication information of uplink transmission. According to a timing relationship specified by the LTE protocol, the terminal may transmit uplink service data needed on a corresponding resource in the fourth subframe after the subframe in which the PDCCH is received. Upon receiving the data packet transmitted by the terminal, the base station may determine whether the data packet is correct by Cyclic Redundancy Check (Cyclic Redundancy Check, CRC for short). In the fourth subframe after the terminal transmits the uplink data, the base station sends indication information indicating whether the data packet is correct. If an error occurs to the data packet, the base station makes the PDCCH of the subframe which carries error information carry a retransmission UL grant of retransmitted data packet simultaneously. The terminal performs a new data transmission according to corresponding retransmission PDCCH information until the terminal receives an Acknowledgment (Acknowledgment, ACK for short) indication sent by the base station, or gives up the retransmission of the existing data packet when the maximum of times of data retransmission is reached.
For downlink data transmission, upon receiving a data packet sent by the base station, the terminal needs to feed back corresponding uplink ACK or Non-Acknowledgment (Non-Acknowledgment, NAK for short) information, wherein there is a mapping relationship between the existing serial number of uplink ACK/NACK and a corresponding PDCCH transmission position of the terminal. The terminal may send the ACK/NACK information on a corresponding uplink transmission resource according to the PDCCH transmission position.
In the existing LTE specifications, each PDCCH schedules resources of one subframe to perform data transmission. Since each newly-transmitted data packet needs a PDCCH resource scheduling indication, in the case that a user channel is stable, frequent change of configuration information of data transmission will cause higher signaling overhead and lower spectrum efficiency.